Hi All,

First post here. I picked up a M8500 the other day and I finally got the help to move it into the house today. I knew that the H. Fail light came on when I got it and I had read a little about seating problems. So I pulled it out and a couple of pins were bent. I straightened those and put it back in and the H.fail light didn't come on again at power up. But no light out of the tubes. I pulled out both power supplies and opened them up. Nothing burnt looking in there. The leds on the low voltage supply don't light up. Are they supposed to?

Any suggestions of what to look at next?

Also, the HDM board (50-2003-07P ISS 1) has a small signal daughter board on it (50-2107-5P ISS 1). Any idea what that is?

Please help.

Michael

Here's a couple of links that might help:

www.etechvideo.com

and

http://www.curtpalme.com/ElectrohomeMarquee.shtm

Also, there's a wealth of info here in this forum as to 'no picture' conditions. Do a search, the problems can range from a bad connection to dead tubes to a bad HV power supply. Do you know the history of the set and the last time it showed a working picture?

Hi Curt,

Thanks for the suggestions. I have downloaded the Mike Parker Maintenance Guide and the CZ Eddie Tear Down procedure.

I have spent some time searching the forums, though not so much for the no picture as for the H. fail. I will continue on with the search.

Should the LEDs on the LVPS be lit when it is powered up?

I don't know much about the history of the projector. It was installed in a very large rear projection setup and used for some kind of stereo/shutterglass 3-D application. It looks very clean with only a little non-point source soot around the HV coupler. Not even much dust in it.

Michael

Do you get HV crackle when you turn the 8500 on.

Try bringing the brightness up to 100 and see if the tubes light up at all. If you are unable to get any light out of the tubes the HVPS may be dead.

I had my HVPS die on my 8000 and it took me a while to figure it out as no error lights came on.

First, do I need a source connected to get a picture?? I thought I could get menus, etc from the remote without a source, but I read a thing that said Barco at least, had to have a source. I can't find my vga to 5 bnc cable at the moment.

I tested the voltages on the board under and behind the right tube and all of them that I could reach with my probe were correct or near correct. The filament voltage read 6.7 VDC. The heaters light up in the tubes. I don't hear anything indicating HV though. Maybe I should try to listen better?

When your HV went bad was there any damage on the board in the HV supply? I opened mine up and I could see anything that looked damaged. Nothing that even looked like it had been warm.

I did have the H. fail light come on again and I pulled the board and reseated the daughter board. It hasn't come on in several starts since then.

Sure would be fun if this thing would work.

Michael

Hello

You do not need a source connected. High voltage makes a crackle/whoosh noise that should be obvious. 6.7v on the filaments is not helpful, it will fry the cathodes in the tubes at some point. Failure of the high voltage section is a possibility.

Thanks for all of the suggestions so far.

I made it quiet in here and tried turning it on again, but now the H. Fail light is back. The board looks very clean with no hot spots that are evident to me. Should I try reheating the solder joints on the mosfets? I might be able to test them in circuit. I will have to look at my tester and see if it can do mosfets. Any other suggestions for problems with the HDM board?

Is there any way, save an ultra high voltage probe, to test the HV power supply? As I mentioned, it looked very clean when I opened it up today. No evidence of big heat.

As background, this is the first crt projector I've looked into, but I do have a fair amount of background in building and repairing vacuum tube audio equipment, so I'm quite familiar with the concept of "healthy respect" for high voltage circuits.

If it gets so far as working I've seen the mod for the tube heater voltage and I am fairly confident I could do it.

One last question, I have hooked it up to my computer via RS-232 and the EH control program communicates with the projector. Is there a program available which will send back operating parameters from the projector to my computer? JVC had something like that in their D-ila projectors. If I just open a port to it with a serial communication program will it send back status messages?

Thanks,
Michael

THe best thing to do is component/board swap. THe E'homes are not known for bad solder joints, but they are known for bad module connections. If hte H board is bad, the HV will automatically shut down, so I'd start by swapping the H board. There's lots of MArquee owners out there, Tim Martin or I are probably your best bet to send the board to for testing/repairing. Try reseating the daughter board first a couple of times, corrosion/oxidation on it's pins can cause that H fail.

If I knew of some boards here in Iowa City I would be happy to try a swap. I'm not sure I'm ready to start shipping stuff off yet. I guess I need to take the lenses off and look at the tube faces at the very least. Is there any way to get an hours of use out of this thing without the display working?

I reseated the daughter board on the HDM again and polished the pins a bit while I had it off. I also removed and reseated the the deflection daughter on the CLM. The H.fail didn't come on again, but I'm still not to confident about it's working properly. Still no picture though. Can I test the voltage output on the connectors that go to the tubes? I have a voltmeter that is good for 1000VAC and up to 250kHz. Well, maybe not a 1000 at 250k. Also have some ten times voltage probes around here somewhere.

Thanks again,
Michael

It seems the H.fail light will not come on at the first cold start, i.e. AC was removed from the projector until startup. It will light after that start if it is left on standby. That makes me wonder if it is related to the CLM and daughter. Not sure why it makes me wonder that though. I think I need to figure out where the horizontal drive signal for that board comes from and look at it on the scope. Yes?? No??

Anyway, I pulled off a couple of the lens this morning and got a couple of pictures of the faces. Does this tell anyone anything about the condition of the phosphor?

I tried to find some history this morning, but was unsuccessful. I know it was used for stereo projection though and that the vertical scan rate is supposed to be set as high as possible. Is that hard on things?

Thanks,
Michael

Another crt face. Taken with flash with crt off. Does it tell anyone anything?

Those tube should be good for a very long time as long as the cathod is not burnt out from the 6.7V.

Chris.

This looks like HVPS failure I had a few years ago on my 8110+. There was no picture or HV and H fail light would sometime come on. Don't get hung up on the diagnostic lights, they are not accurate.

Well, so possible good news on the crt's then.

I just measured the backup battery voltage and it is 3V. I thought maybe a loss of memory between startups was behind the cold start and standby start behavior. It seems to be good though.

I've been considering the HV supply too. There are so many conditions that inhibit it though, that I can't see anyway to prove it.

Michael

I tested the H drive signal going to the HDM board and found a square wave at around 30kHz that was 40mV peak to peak. Seems right for being there and right for frequency. I don't know how large it should be though. Anybody?

Michael

Do you have HV crackle.

It sounds like a dud HVPS to me.

I'm not sure how to safely test the HV output, but if you have no fear of high voltage I can give you some easy ways to check it.
(You have a chicken and jumper cables, right):eek::D

Erik

I might be leaning toward HVPS myself. I'm trying to figure out where I can hook into the HV inhibit signal to see if it ever goes low or not. If it doesn't then the HV is never getting turned on and it's back in one of the boards.

A chicken and jumper cables you say? Might be doable. I have an electrosurgery unit with the operator's manual and the training procedure is to use it on a room temperature steak, preferably flank IIRC. I toyed with the idea of a cook and cut knife transformation.

I'm not really set up to try to measure HV output myself. I toyed with the idea of dragging a bench supply and the HVPS down to the local tv repair shop and seeing if they would do it for a couple of bucks.

Michael

I tried to find some history this morning, but was unsuccessful. I know it was used for stereo projection though and that the vertical scan rate is supposed to be set as high as possible. Is that hard on things?

Thanks,
Michael

One does not "set" the refresh or resolution of a CRT projector; the projector reacts and sets itself to incoming signals.

If the model number has "-ST" then the unit was built with P43 fast refresh phosphor.

It's not an ST model. It was part of a Pyramid system and rear projected onto a screen that was 66"x50". I assumed they were talking about the source rate.

I have done a little more testing this morning.

1. I found the Hdrive seems to be around 2.5V square wave and around 25kHz. My scope isn't calibrated so all the numbers are a little iffy.

2. I don't have a voltage probe for the output of the HDM board to the deflection yokes, but I put a current probe on and tested all three colors. I have attached a waveform. It seems to be in the 3 amp peak area, but that is an iffy guess.

3. The EHT-inhibit on the VIM goes to 11.45V on power up and never comes down. So I guess the HVPS is inhibited from turning on.

4. The Scan fail pin on the VIM goes to +5V whether the H.fail light comes on or not. It doesn't go to 0 in any case. I'll assume this means some problem with the HDM board though I think the same condition will occur with a Vertical Scan failure too.

5. Band-switch on the VIM goes high, then low, then high, and then low and stays low. I think this means that the VIM is looking for input and then switching to internal video and locking onto that.

6. If I start from a no AC plugged in condition the H.fail light doesn't come on. If I start from standby it does come on. It appears to take a couple of minutes unplugged for the transition to happen.

That's it for now.

1. Can anyone comment on the deflection waveform shape? I don't know what it is supposed to look like, but I would assume it is some sort of ramp.

2. Assuming the output of the HDM is correct, any idea what part would be giving a scan fail signal?

3. Any other ideas?

Thanks,
Michael

Hello

You could have any of seven different problems here. A bad rail from the low voltage could hold everything down. A shorted device on any board. A bad H or V sweep board. A neckboard problem (try unplugging the 14 pin umbilicals). A foreign metallic object somewhere causing a short (screw or bolt).

He-he, only 7 things? :rolleyes:

I think I've tested all the rails now and I checked the 2.5V reference on the HDM and they all seem ok. The output from the scan error amp is 0V, but the output from the fet after it is 5V. I'm trying to figure out if that is right or not. I'm not too smart in that area.

Did the current waveforms for the horizontal deflection look reasonable?

I guess I take apart a few more connectors and replug them and see if that does anything. I'm still confused by that fail light after standby but not before. Well, that's not the only thing I'm confused by, but I'll leave it at that for now and stay on topic.

Michael

Check that all the belly fans are Ok and that no separate Low voltage lead is grounded or short circuit. Belly fan leads have touched the chassis in two cases to my knowing causing the HV not to start and a failure light in back of the PJ.

I have done a little more testing this morning.

1. I found the Hdrive seems to be around 2.5V square wave and around 25kHz. My scope isn't calibrated so all the numbers are a little iffy.

That's close. Without a video input the projector should run at 31.5KHz. That drive signal should be 4 or 5Vpp.

2. I don't have a voltage probe for the output of the HDM board to the deflection yokes, but I put a current probe on and tested all three colors. I have attached a waveform. It seems to be in the 3 amp peak area, but that is an iffy guess.

The current is about right but wrong shape. See attachment

3. The EHT-inhibit on the VIM goes to 11.45V on power up and never comes down. So I guess the HVPS is inhibited from turning on.

Yep

4. The Scan fail pin on the VIM goes to +5V whether the H.fail light comes on or not. It doesn't go to 0 in any case. I'll assume this means some problem with the HDM board though I think the same condition will occur with a Vertical Scan failure too.

Yes. The H and V sweep fail signals are monitored on the vert defl card. Scan fail is high if either is bad.

5. Band-switch on the VIM goes high, then low, then high, and then low and stays low. I think this means that the VIM is looking for input and then switching to internal video and locking onto that.

It goes through some changes during start-up. Band-switch goes high to shut down the horizontal deflection so relays and timing capacitors can be switched in and out for different scan rates.


1. Can anyone comment on the deflection waveform shape? I don't know what it is supposed to look like, but I would assume it is some sort of ramp.

Should be ramp.


Thanks,
Michael

It might be worth a check of the big mosfets mounted to the heatsink on the HDM. Measure ohms across the outside legs. If it's only a few ohms then that part is shot.

Scott

Scott,

Thanks for the info. Your picture of the waveform looked like I could have expected it should be. I wonder what is causing that extra kink in mine? I'll try the ohmmeter on the Mosfets tomorrow. Any other suspect parts? Or should I say other parts to suspect?

Thanks,
Michael

I measured the dcr between the outer two legs of the 3 large mosfets on the heatsink and they all read 8kohms with the probes in one direction and 6.4kohms with the probes reversed. The two smaller ones read more like 100 ohms. The two smallest ones I didn't test. I'm not sure what they are.

Michael

As I meander along with this project. I tested quite a few of the transistors on the HDM and it's daughter today and they all tested good. Except the power mosfets. My tester apparently can't do that type. Since they are switches in the flyback and I have current to the yokes I'm assuming they are working. Whether they are working right is another question. The distortion in the waveform continues to baffle me.

I tested the V fail going into the HDM board and it was low, which I believe indicates no failure on the vertical sweep board.

I found that the H. fail light came on if the projector was on standby and the HDM board was inserted right before power up. If it is cold started the H. fail doesn't come on. This makes me wonder what parts are getting power during standby. Since the VIM board is the one that last passes the scan fail signal to the Control Module and also controls the HV inhibit I'm starting to wonder if I should look a little more in that direction? I don't think the Control module actually controls either of those functions, I think it just translates it to the indicator leds.

Will a Marquee power up without a VIM installed? Without damage that is?

I tested the leakage to the chassis today too. It was some milliamp or so. I think that probably tells me that the fans wires aren't shorting to the chassis. As an aside, my line was over 128V all afternoon. Annoying.

Progress, no breakthroughs.

Michael

Will a Marquee power up without a VIM installed? Without damage that is?


It powers up (fans running) but it doesent start HVPS if VIM is not installed.

Man, you're all over the place.

I'll make a few suggestions here, and if they don't work for you, It's then time to send some stuff off to others (Tim, Curt) to either check out or repair for you.

You will not be getting much help in playing around with that HVPS. It's best to stay away from it, because it's not a repairable item. And the risk of damaging it or creating a potential hazard for yourself is higher than you stumbling across a fix for it (if it's the problem). So that Item is a swap or have tested item. And don't wast your time taking it to a TV shop. That would be very similar to taking a jet engine to your auto mechanic.

If you have the pulse on the HDM, then from there check for vertical pulse on the three yoke connectors on the vertical board. If the pulse is present on all three connectors, move on to the VIM. The only test you can do on the VIM is check the two green fuse's on the 5 volt rail (right at the connector).

If the two fuses are good - the HVPS is suspect.